Examples of top drive well drilling apparatus are illustrated in U.S. Pat. Nos. 4,421,179; 4,458,768; and 4,605,077. These top drive systems use a motor in combination with a gear housing. The motor rotates an output shaft. A pinion gear is mounted on a lower end of the output shaft. This pinion gear is engagable with a large diameter ring gear which is disposed in the gear housing. A tubular driven shaft, to which sections of pipe may be attached, is secured to and rotates with the ring gear.